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Summer 2008

Advanced Biomagnetic Imaging at UCSF

One of the most effective resources that the UCSF Pediatric Epilepsy Center offers its young patients is access to a state-of-the-art, whole-head magnetoencephalography (MEG) machine. The MEG machine, housed in the UCSF Biomagnetic Imaging Laboratory (BIL), records the magnetic fields produced by neuronal activity in the brain. These signals, in turn, are used to create computer models of both the time course and the spatial patterns of this activity.

MEG imaging offers distinct advantages over more traditional forms of brain imaging. Unlike EEG recordings, for instance, MEG recordings are not hampered by the skull, blood and tissues surrounding the brain, and MEG can record from the whole brain simultaneously. Unlike MRI, which reveals only brain structure, MEG directly records brain activity. Heidi Kirsch, M.D., medical director of the BIL and assistant professor of neurology and radiology, points out that in addition to abnormal brain activity, such as that produced by a seizure focus, MEG can locate brain regions that have motor, sensory and language functions.

Used together, MEG and MRI allow neurophysiologists and radiologists to pinpoint the source of seizure activity in the brain more precisely, and also to map out functional areas that are important to avoid during surgery. "We can actually lay reconstructions of brain activity derived from MEG over the MRI and provide the surgeons with a map that shows functional landmarks on the child's brain," says Sri Nagarajan, Ph.D., director of the BIL and professor of radiology. "This is crucial information in the surgical suite."

MEG imaging also has special advantages for the Pediatric Epilepsy Center's young patients. The imaging device surrounds the head like an old-fashioned hair dryer, and in contrast to MRI, the patients do not have to lie perfectly still in a loud tunnel. In fact, it's so quiet that many children fall asleep during the scan.

For optimal results, parents are counseled to keep their children awake before the MEG session. "The brain produces more abnormal activity when the child is asleep anyway," Nagarajan says. "So keeping the patient awake before the scan, and letting the child fall asleep for the scan, allows us to pick up abnormal signals more easily."

The UCSF Department of Radiology has had an MEG machine since 1992, and upgraded it in 2004. In addition to using the machine clinically in patients with epilepsy and with brain tumors, researchers at UCSF are developing cutting-edge algorithms and computer modeling to measure neuronal activity in the brains of children and adults with brain injuries, autism and other neurologic disorders.

For more information about MEG, or to schedule an MEG study, contact the UCSF Biomagnetic Imaging Laboratory at (415) 476-6888.

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